Thermoelectric generators (also sometimes referred to as “TE generators” or “thermogenerators”) are devices which convert heat (temperature differences) directly into electrical energy, using a phenomenon called the “Seebeck effect” (or “thermoelectric effect”).
Older such devices used bimetallic junctions and were typically more bulky than desired. More recent such devices use semiconductor p and n junctions, such as of bismuth telluride (Bi2Te3), lead telluride (PbTe), or other materials such as known in the art and can have thicknesses in the millimeter range. These are typically solid state devices and unlike dynamos have no moving parts, with perhaps the occasional exception of a fan.
Thermoelectric generators are generally constructed from pairs of thermoelements, usually heavily doped p- and n-type semiconductors, connected electrically in series but thermally in parallel. One thermal connection is to a heat sink, and the other to a heat source. An electrical current across a load connected in series with the generator can be produced if there is a temperature difference between the heat source and the heat sink.
The Figure of merit (ZT) commonly used to measure the efficiency of a thermoelectric (TE) material is given by:ZT=(α2/κρ)T  (1)where T is the average operating temperature in Kelvin (K), α is the material's Seebeck coefficient in Volts/K, κ is the material's thermal conductivity in Watts/(m·K) and ρ is the material's electrical resistivity in Ohm·m2. The ZT is a material property, and is not affected by device design.
Thermoelectric generators are solid state heat engines and can provide electrical power from any heat source that is above the ambient temperature of the surroundings. Thus, rather than relying on the purchasing and supplying of fuel, a thermoelectric generator can provide its fuel from any device or machine that creates and releases substantial amounts of heat, e.g., what in many cases would more commonly be referred to as “waste heat.”
In many situations involving energy harvesting from waste heat with thermoelectric generators, however, the thermal gradients (often called ΔT) can be small. Bierschenk, in “Optimized Thermoelectrics For Energy Harvesting Applications,” Ch. 12 in Energy Harvesting Technologies, ed. by S. Priya and D. J Inman, Springer, 2009, has described various advantages that can be realized via the use of high-junction number, high-aspect ratio thermoelectric generators in such applications.
In view of the above, there exists a need and a demand for such high aspect ratio thermoelectric generator devices as well as methods or techniques to produce or manufacture such thermoelectric generator devices.